If the orthocentre of the triangle formed by the lines 2 x+3 y-1=0, x+2 y-1=0 and a x+b y-1=0, is the centroid of another triangle, whose…

If the orthocentre of the triangle formed by the lines $\displaystyle 2 x+3 y-1=0, x+2 y-1=0$ and $\displaystyle a x+b y-1=0$, is the centroid of another triangle, whose circumcentre and orthocentre respectively are $\displaystyle (3,4)$ and $\displaystyle (-6,-8)$, then the value of $\displaystyle |a-b|$ is $\displaystyle \_\_\_\_$.